1. Field of the Invention
This invention provides an instrument for measuring the number concentration and particle size distribution of ultra-fine particles with less than 0.1 micrometer diameter suspended in gas.
2. Prior Art
The conventional instrument for measuring gas-laden particles with the same extremely small size is the "electrical mobility analyzer" in which the particles are precharged and pass through a DC electric field for separation of charged particles according to their electrical mobility. The detection of the particles in this type of instrument is made by measuring the very low DC current carried by the separated charged particles.
In the conventional instrument described above, the level of the detected current carried by the charged particles becomes so small, when the particle size is extremely small, say less than 0.1 micrometer, and its number concentration is very low, that its measuring error becomes excessively large, finally to make a reliable measurement impossible.